The use of insensitive munitions explosives (IMX) is increasing as the U.S. Army and other armed forces seek to replace certain conventional munitions for improved soldier safety. The IMX formulations are more stable and less prone to accidental denotation while designed to match the performance of legacy materials. Two formulations of IMX are currently being produced; IMX 101 is qualified as a replacement for trinitrotoluene (TNT) in artillery rounds while IMX 104 is a replacement for composition B and may be used in mortar rounds.
The development of IMX compounds and then expanding use results in the need for a simple detection method for the four constituents of IMX-101 and 104; 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), 1-nitroguanidine (NQ), and Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX).
The standard environmental test method, U.S. EPA method 8330, for nitroaromatic, nitramine, and nitroester analysis of conventional munitions compounds uses high performance liquid chromatography (HPLC) separation and detection by ultra-violet absorption. The target analyte list for U.S. EPA method 8330 contains 17 components: 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 3,5-dinitroaniline, 1,3-dinitrobenzene 2,4-dinitrotoluene, 2,6-dinitrotoluene, Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), nitrobenzene, nitroglycerin, 2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene, [3-Nitrooxy-2,2-bis(nitrooxymethyl)propyl]nitrate (PETN), RDX, N-methyl-N2,4,6-tetranitroaniline(tetryl), 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene. Variations of this method can use electrospray ionization mass spectrometry (ESI-MS) or tandem mass spectrometry (MS-MS) for detection and quantitation of these constituents.
An alternative U.S. EPA method 8095, uses GC-ECD to quantify all of the target compounds m method 8330. However, three of the IMX constituents, NTO, NQ and DNAN, are not currently on the target analyte list of either EPA method 8330 or 8095. Of those three, only DNAN has been shown to be separated from concomitant compounds under the conditions of the U.S. EPA method 8330. In other words, neither U.S. EPA method 8330 nor U.S. EPA method 8095 has any effectiveness for separating NTO and/or NQ from concomitant compounds. Accordingly, both U.S. EPA method 8330 and U.S. EPA method 8095 are of little or no use when looking to provide analytical evaluation of soil samples, aqueous samples such as ground water samples and tissue samples containing insensitive munitions explosives (IMX).
There is currently a need for a simple method which efficiently separates and quantifies insensitive munitions constituents and legacy compounds on a single HPLC column. Previous work has focused on either the separation of individual IMX munitions constituents or the separation of one component and its derivatives. Consequently, the detection methods presently available utilize multiple columns for the analysis of IMX munitions constituents, thereby not only adding complexity but also extending the analysis time and cost of analysis.
Previous work has utilized a two column approach in order to quantify the individual components of the IMX family of compounds. The two column approach has been documented in dissolution studies of NTO from IMX compositions. The researchers used a Thermo Scientific Hypercarb column with an acidified eluent mixture for the analysis of the highly water soluble components, NQ and NTO, and a Dionex Acclaim® E1 column under EPA method 8330 conditions for the analysis of RDX and DNAN. The separation of NQ and DNAN in the presence of RDX has been demonstrated by ultrafast liquid chromatography. NTO and its derivatives have been analyzed by HPLC and capillary electrophoresis.